After IC chips are formed on a semiconductor wafer (hereinafter, referred to as “wafer”), a probe test is performed on the wafer by using a probe apparatus in order to inspect electrical characteristics of the IC chips. The probe apparatus is configured to control a position of a wafer chuck (wafer mounting table) which is movable in X, Y and Z directions and rotatable about a Z axis so that probes, i.e., probe needles, of a probe card are brought into contact with electrode pads of the IC chips of the wafer, the probe card being provided above the wafer chuck which mounts thereon the wafer.
In order to make the probes precisely contact with the electrode pads of the IC chips on the wafer, a so-called fine alignment is performed in advance and, then, the result therefrom is used to obtain a precise location of the wafer chuck at which the probes contact with the electrode pads of the IC chips, e.g., precise coordinates of a driving system managed by a pulse encoder interlocked with a driving motor for driving the wafer chuck. Moreover, the coordinates of the driving system may be determined by optical information corresponding to the count number of pulses obtained from slits formed on linear scales provided respectively on an X stage moving in an X direction, a Y stage moving in a Y direction and a Z stage moving in a Z direction.
In order to perform the fine alignment, it is preferable to employ a configuration in which a camera is provided to have a downward view to image a wafer at a moving body moving horizontally between the wafer chuck side and a probe card and, also, a camera for taking an image of probes is provided at a wafer chuck side (see, e.g., Japanese Patent Laid-open Publication No. 2001-156127). This is because when the images of the wafer surface and the probes are taken after focuses of both cameras are aligned, the images look effectively same as the ones that the wafer surface and the probes were imaged by a single camera. Further, in order to obtain a map of chips on the wafer, it is required to perform an operation for obtaining a central position of the wafer (coordinates of a driving system of a wafer chuck) by imaging, e.g., four points in a peripheral portion of the wafer, by the camera for imaging the wafer and an operation of obtaining a orientation of the wafer by taking images of specific points on the wafer, e.g., two IC chips spaced from each other.
After the orientation of the wafer is adjusted, specific points on the wafer are imaged and, then, the position of the wafer chuck (a so-called contact position) at which the electrode pads of the IC chips contact with the probes is obtained with high accuracy based on the imaging result. In order to perform the fine alignment, the moving body is positioned at a preset location and, then, the wafer chuck is moved so that each point on the wafer can be imaged sequentially by the camera for imaging the wafer. However, to image a large number of points, a total period of time required for moving the wafer chuck increases. Besides, since the movement region of the wafer chuck is large, the probe apparatus main body needs to be designed at a dimension capable of covering the movement region, thus scaling up the apparatus. Especially, as the wafer is scaled up, there is expected a wafer having a dimension greater than 12 inches. Therefore, if the number of probe apparatuses to be installed increases, a large occupation area is required. However, if a region of the clean room is restricted, it is not possible to increase the number of probe apparatuses to be installed.